Signaling the potential for an important policy reversal, Environmental Protection Agency Administrator Lisa Jackson said in a congressional hearing on Tuesday that the agency would consider revisiting its controversial position that a popular natural gas drilling technique doesn't harm groundwater.

A 2004 study (PDF) conducted by the EPA concluded that hydraulic fracturing -- a process that involves pummeling the earth with millions of gallons of water mixed with sand and chemicals to extract natural gas -- causes "no threat" to underground drinking water.

The study is often used by the gas industry to rebut concerns over drinking water contamination. It was also the main basis for a provision in a 2005 energy bill that exempts hydraulic fracturing from regulation under the Safe Drinking Water Act. The bill says the process is exempt because it doesn't harm groundwater. Opponents of the exemption are trying to repeal it, and a new study from the EPA would add muscle to their argument.

A ProPublica investigation co-published with BusinessWeek last November identified serious flaws in the EPA's 2004 study. We found that the agency negotiated directly with the gas industry before finalizing its conclusions and ignored evidence that the process might indeed contaminate water supplies.

Rep. Maurice Hinchey (D-NY) expressed concern about these issues and recent reports of contamination near drill sites. At a House Appropriations Subcommittee on Interior hearing on Tuesday, he asked Jackson whether the emerging evidence would prompt the EPA to revise its previous conclusions.

Jackson said she recognized that the current regulations restrict the EPA's ability to protect groundwater and said the issue "was well worth looking into." But she didn't say how the EPA would approach the problem or whether the 2004 study would be revised.

A spokesperson for Jackson would not elaborate on her remarks.

The statement has stirred optimism among environmentalists who have been urging the EPA and Congress to repeal the exemption. They feel it's a sign that the Obama administration is willing to take a fresh look at the Bush administration's legacy on gas drilling.

"Big ships turn slowly," said Bruce Baizel, an attorney with the Oil and Gas Accountability Project, "but I think this is the first time EPA has acknowledged that maybe their previous conclusions were not entirely supported by sound science."

Industry representatives contend that fracturing is safe and dispute the claim that the process has been linked to water contamination. They also maintain that fracturing is best regulated by individual states, rather than the federal government.

"The EPA study is one of several studies done by a variety of different interests in the past decade, and I don't believe that there is any compelling evidence that the risk has changed since 2004," said Lee Fuller, vice president of government relations for the Independent Petroleum Association of America. "The reports mentioned (in the hearing) have been analyzed to show that they are not related to hydraulic fracturing."

The promise of abundant natural gas is colliding with fears about water contamination.

The Story So Far

The country’s push to find clean domestic energy has zeroed in on natural gas, but cases of water contamination have raised serious questions about the primary drilling method being used. Vast deposits of natural gas, large enough to supply the country for decades, have brought a drilling boom stretching across 31 states. The drilling technique being used, called hydraulic fracturing, shoots water, sand and toxic chemicals into the ground to break up rock and release the gas.

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